Over 4M at risk of severe weather in Texas; winter storm warning in Colorado: Tuesday forecast

The Upper Midwest and northern Plains were bracing for historic river flooding Tuesday, where some areas could see the worst in 20 years. Meanwhile, severe storms were possible across portions of Texas on Tuesday afternoon and evening.

"A one-two punch of severe weather is in store across the southern Plains both Tuesday and Wednesday," AccuWeather Meteorologist Brandon Buckingham said.

In Texas, more than 4 million people were under a severe weather threat Tuesday.

And Colorado isn't free from wintry conditions yet. A winter storm warning was issued in parts of the state.

Here's what to know about the national weather forecast for Tuesday.

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Risk of thunderstorms, tornadoes in Texas

The National Weather Service said severe thunderstorms will be possible over parts of central and northern Texas on Tuesday, which could bring hail and "perhaps a couple of tornadoes."

"Any thunderstorms that can form across this region would probably become severe and pose a threat for large to very large hail and damaging winds," the weather service said. "However, uncertainty remains rather high regarding the number of severe thunderstorms that may form. The risk for a couple of tornadoes may also increase with this activity late Tuesday."

Multiple tornado warnings were issued Tuesday night in parts of northwestern Texas and a potentially significant tornado was located over Southern Dickens County, moving southeast at 25 mph. The National Weather Service advised residents to take cover, calling it a "life-threatening situation" due to flying debris and destructive conditions.

More than 4 million people are under a "slight" risk for severe weather – the second of five risk categories for the National Weather Service – in Texas, including the cities of:

• Austin

• Waco

• Abilene

• Wichita Falls

Flood warnings around Mississippi River 'until further notice'

River flooding is ongoing this week across the Upper Midwest, which could be some of the region's worst river flooding in over 20 years, forecasters say.

The weather service has issued flood warnings in several states along the Mississippi River, including Minnesota, Wisconsin and Iowa, "until further notice." Motorists in affected areas are advised to not drive around barricades or through flooded areas.

The flood warnings come "due to a combination of snowmelt run-off and recent rainfall," the weather service said.

Flood warnings were also in effect along the Red River in North Dakota and Minnesota.

Winter storm warning in Colorado mountains

A significant winter storm is expected to bring heavy snowfall to Colorado's mountains, foothills and Palmer Divide region in the central part of the state Tuesday afternoon through Wednesday morning, according to the National Weather Service.

Snowfall upward of 2 feet is possible in some areas, including the higher elevations of Park, Jefferson, Clear Creek, and Gilpin counties. In lower elevations, scattered rain showers and a few thunderstorms are expected Tuesday.

Red flag warnings in Southwest as temperatures rise

Red flag warnings will be in effect once again in the Southwest, stretching from southeastern Arizona through western Texas. Tuesday is expected to be a high fire danger for the affected areas, with wind gusts up to 35 mph mixed with low humidity resulting in "critical fire weather conditions."

Temperatures will also be in the high 80s to low 90s in the area.

"These dry conditions, combined with low relative humidities and gusty winds will keep the fire weather threat at an elevated to critical level over the next few days across large portions of New Mexico, far southeastern Arizona and southwest Texas," the weather service said.

National weather radar

Follow Jordan Mendoza on Twitter: @jordan_mendoza5.

This article originally appeared on USA TODAY: Colorado winter storm warning; Texas at risk of storms, tornadoes